The number of communications terminals capable of accessing non-3GPP access networks for technologies such as Wireless Local Area Network (WLAN) or Worldwide Interoperability for Microwave Access (WiMAX), in addition to 3GPP access networks, continues to increase. Such communications terminals may be able to automatically select a particular access network based on information such as user settings, operator policy and network conditions, for example.
In an effort to standardize the behavior of such terminals and address new issues related to the integration of non-3GPP access technologies and 3GPP access technologies, new functionality known as Access Network Discovery and Selection Function (ANDSF) has been introduced by the 3GPP in Release 8. The ANDSF is an entity within an Evolved Packet Core (EPC) of the System Architecture Evolution (SAE) for 3GPP compliant mobile networks.
ANDSF provides communications terminals (also known as user equipment) with access network related information in order to control access to access networks. This provisioning may assist the communications terminals in performing access network discovery or access network selection, for example. There are currently four main types of access network related information that an ANDSF control apparatus may provision to a communications terminal:
Inter-System Mobility Policy (ISMP)
ISMP information is a set of operator-defined rules and preferences based upon which a communications terminal may make inter-system mobility decisions. Communications terminals use the inter-system mobility policies when capable of routing IP traffic only over a single radio access interface at a given time.
Access Network Discovery Information
Access network discovery information may include a list of access networks available in the vicinity of the communications terminal. These may be limited to those of a particular access technology types (e.g. WLAN, WiMAX, etc.) requested by the communications terminal.
Inter-System Routing Policy (ISRP)
ISRP information may include a list of policies provided in order to meet operator routing/offload preferences on distribution of traffic of a UE (communications terminal) for transmission over access networks used by the UE. Communications terminals use the inter-system routing policies when capable of routing IP traffic simultaneously over multiple radio access interfaces.
Inter-APN Routing Policy (IARP)
IARP information may include validity conditions, filter rules, priorities and the like for Inter-APN routing.
For details of the functionality of the ANDSF, see the 3GPP specifications TS 23.402 V12.2.0 (especially chapter 4.8.2.1) and TS 24.302 V12.2.0 (especially chapter 6.8 and Annex A.2).
Access network related information is transferred between the communications terminals and the ANDSF using Open Mobile Alliance (OMA) Device Management (DM) as defined in OMA-ERELD-DM-V1_2 (chapter 5 lists the specification baseline of OMA DM device description Baseline) with an ANDSF Management Object (MO) as specified in the 3GPP specification TS 24.312 V12.2.0. The ANDSF MO is a hierarchical tree of nodes used to describe above described access network related information stored in a communications terminal. A portion of the ANDSF MO may be provided to the communications terminal, possibly based upon information such as the current location of the communications terminal, for example.
However, the current technique for providing access network related information is space inefficient and requires large amounts of memory for storage of the information. As the size of the ANDSF MO increases, ever growing network payloads are required for the transmission of the access network related information between the ANDSF control apparatus and communications terminals. Therefore, there is a need for techniques to make the provisioning of access network related information more efficient.